As communication technology develops, broadband communication services, such as Asymmetrical Digital Subscriber Line (ADSL) services, Very-high-speed Digital Subscriber Line (VDSL) services, etc., may be provided through local telephone cables that originally bore traditional narrow-band communication services such as Plain Old Telephone Service (POTS)/Integrated Services Digital Network (ISDN) services; for example, ADSL over POTS, ADSL over ISDN, VDSL over POTS, VDSL over ISDN services, etc., may be provided. By now, those services have been widely used all over the world. For convenience of description, hereinafter digit subscriber lines, such as ADSL, VDSL, and Single-pair High-bit-rate Digital Subscriber Line (SHDSL), are referred to as xDSL collectively.
As shown in FIG. 1, xDSL signals and POTS/ISDN signals coexist in the same external subscriber line; at the Central Office (CO) side, a splitter (SPL) in a Digital Subscriber Line Access Multiplexer (DSLAM) separates xDSL services and POTS/ISDN services, and sends xDSL services and POTS/ISDN services to an xDSL service board and a POTS/ISDN service board respectively for processing; and at the Customer Premises Equipment (CPE) side, the SPL sends the xDSL services and the POTS/ISDN services to a Remote Terminal Unit (RTU) and a telephone, respectively.
To ensure normal operation of xDSL services, it is required to detect any fault that may affect the services; therefore, the subscriber line parameters, the CPE, the CO device, etc., should be measured. The subscriber line parameters include line voltage, line resistance, line capacitance, line background noise, line-earth balance, etc.; the CO device includes a DSLAM port, a Broad-Band Access Server (BRAS), a Dynamic Host Configuration Protocol (DHCP) server, etc. With the results of the measurement, the operation of the subscriber line, CPE and CO device may be ascertained, and any fault that may affect service operation may be located and eliminated in a timely way.
FIG. 2 shows a schematic diagram illustrating test access in an xDSL service network. In FIG. 2, there is shown a Personal Computer (PC), an RTU, a Main Distribution Frame (MDF), a DSLAM, a BRAS in the xDSL service network, the Internet, and a Broadband Test Unit (BTU) for test purpose. It can be seen from FIG. 2 that when the line, CPE, and CO device are to be tested, a test device, e.g., a BTU, should be connected to the xDSL service network, and such a connection shall not affect normal service operation.
However, most existing DSLAM devices are different from narrow-band switches in that they do not provide a test bus and do not support access function, i.e., they may not connect a line or the like of a tested subscriber to a test device automatically in response to a control command; therefore, it is quite difficult to implement automatic test of the DSLAMs and associated subscribers. How to settle subscriber test access for a DSLAM without a test bus and design a good automatic access method and system has significant effect on operation and maintenance of broadband services and thereby Quality of Service for the services. The following two technical solutions are employed in the prior art.
Solution 1: interpose an access device between an MDF and a CO DSLAM.
As shown in FIG. 3, an access device, usually referred to as an external access matrix, is interposed between existing MDF and CO DSLAM.
The external access matrix is connected in series on the subscriber line, and shall not affect normal operation of subscriber services when there is no test to be performed. In addition, upon test, the external access matrix connects automatically a tested subscriber to a test module for test in response to a command from the control system. After the test, the external access matrix automatically releases the tested subscriber in response to a command from the control system so as to restore the line to a connection state for normal operation of services. Here, the “tested” subscriber refers to a CO device port, a line, CPE or the like.
However, in the above solution 1, for a DSLAM without a test bus, the input ports of the external access matrix shall be in a one-to-one relation to the subscribers to be tested. As a result, the higher the number of subscribers is, the larger the access device will be, and thereby the larger the equipment room area will be occupied, the higher the cost will be, and the higher engineering workload and the more complex engineering will be caused. In addition, since the external access matrix should be connected in series in an original network line, a long service downtime is needed during installation, making the services unavailable, Quality of Service for the services degraded, customer satisfaction to the operator decreased, and the operator's earnings reduced.
Solution 2: add an access matrix in a DSLAM frame.
As shown in FIG. 4, an access matrix is added in a DSLAM frame, i.e., an access matrix board is added in series between an SPL board and an external subscriber line.
The access matrix board is connected in series on the line and shall ensure normal operation of subscriber services when there is no test to be performed. Upon test, the access matrix board connects automatically a tested subscriber to a test module for test in response to a command from the control system. After the test, the access matrix board automatically releases the tested subscriber in response to a command from the control system so as to restore the line to a connection state for normal operation of services.
However, since the access matrix board should be connected in series in an original network line, a long service downtime is needed during installation, making the services unavailable, Quality of Service for the services degraded, customer satisfaction to the operator decreased, and the operator's earnings reduced. Furthermore, due to the fact that an existing xDSL subscriber board is high in density, the corresponding access matrix board has to be large and may not be installed in a DSLAM cabinet if the DSLAM cabinet is not reconstructed, making the installation relative complex.